Plant lectins have become major tools in studies of the protein- carbohydrate interactions that play a key role in establishing the specificity of a wide variety of biological recognition and communication events. These carbohydrate binding proteins have also been used for a variety of medical purposes, including blood typing, separation of populations of lymphocytes prior to bone marrow transplantation, targeted drug delivery and various diagnostic assays. It is the long term goal of this research to determine the relationship of plant lectin structure to function. Such information should enhance the utilization and versatility of lectins as tools, provide basic information on protein-carbohydrate interactions and ultimately yield clues leading to the elucidation of the role of these proteins in the plant. This investigation focuses on the class of N-acetylgalactosamine/ galactose specific lectins and will use the family of lectins from the legume, Doliclios biflorus, as a model experimental system for exploring the relationship of lectin structure to function. This study will also include the separate adenine binding sites which have recently been found in a number of plant lectins. The specific aims of this proposal are: l) to further define the structural prerequisites for carbohydrate and adenine binding and specificity of the seed lectin and a related vegetative tissue lectin, DB58; 2) to study the regulation and modulation of lectin activity, including site-site interactions, subunit interactions, and the effects of posttranslational modifications; and 3) to continue studies of the structures and activities of DB46 and DB57, two related novel N-acetylgalactosamine binding lectins found in the vegetative tissues of this plant. This study will employ a variety of methodologies, including the use of site-specific mutations and lectin chimeras to probe the effects of localized structural alterations on lectin activity.